passive equilibrium as control

CSGnet Archive CSG1996
1

[From Mr. Remi Cote 18194.090896 EST

--Bill Powers (960807.0700 MDT)]

Is A glass of water a purposive, control system?(in my example)

No, it is not. The reason is that it has no internal store of energy

that is used in opposing a disturbance. All the energy that is used in
correcting the level of the water comes from the disturbance.

What about the energy contained in the structure of the glass. The

resistance of that structure is a kind of energy.

The energy comes from outside the system.

By the same means we can show that a pendulum is a passive equilibrium
system and not an active control system. When you push a pendulum to one
side, you increase its potential energy: the stored energy comes from
the push that disturbs the pendulum. No energy comes from the pendulum itself;
it all comes from the disturbance.

Another example of control that you can label passive equilibrium
is the flying wheel of steam machine. When the speed of a rotating axe
(shaft) is high enough, the centrifuge force grasp the iron ball (wich
is forged to a control arm). The resultant is the release of
steam when the speed is too hight.

Here also there is resistance, from the structure of the iron ball.
Here also the energy came from the outside. Is this example too
a passive equilibrium system?

When
we say that a system is "passive" we mean that has no energy source
independent of the disturbance; it moves or changes only as external
influences make it move or change.

What if (or suppose) that living organism are Hierarchical passive
equilibrium system, it could be an interesting view of behavior at work.

That's the point of my reflexion here...

2

[From Bruce Abbott (960812.2030 EST)]

Mr. Remi Cote 18194.090896 EST --

What about the energy contained in the structure of the glass. The
resistance of that structure is a kind of energy.

Press the palm of your hand against the wall and push HARD. The pressure
exerted by your hand is transmitted into the wall, bending the surface
inward slightly, elastically compressing the material on the near side and
stretching it a bit on the back side. The force of your push does work on
the wall, storing energy in the wall until the counterforce generated by the
repulsion or attraction of the compressed/stretched bonds equals that being
developed by your hand. All the energy going into this passive resistance
comes from your push.

Now press the palm of your right hand into the palm of your left hand. As
you press, try to prevent your right hand from moving your left hand.
Slowly increase the pressure exerted by your right hand while still
attempting to keep your left hand from moving. What happens to the muscles
in your left arm as you push harder or softer against the left palm?

Superficially the two situations -- pressing against the wall and pressing
against your left palm -- look the same, but they are fundamentally
different. The wall has no reference for being where it is; furthermore,
all the energy necessary to resist the pressure from your push comes from
your push via the work it does in stretching/compressing the wall material.
The energy necessary to prevent your push from moving your left hand comes
from the muscles in your left arm and shoulder. Those muscles contract
because you have set a reference for left hand position, the pressure
exerted by your right palm against the left generates a small error between
reference and actual left hand position, and this small error signal
switches on the process by which chemical energy stored in the muscle (and
transported there via the bloodstream) generates contractile forces that act
to oppose further motion of your left hand.

The energy used to oppose the push of your right hand comes not from work
done in compressing your left palm (the disturbance), but from the release
of chemical energy in the muscles.

One of my favorite sci fi scenes is the one in Forbidden Planet when our
heros have sought safety within a vault constructed of indestructible Krell
metal, while outside a Freudian Monster From the ID, unwittingly summoned by
the good Doctor What's-his-name's mind (I've forgotten!), tries to break
through, powered by the heat of the planet, the energy being shunted into
the Krell through millions of klystron power relays. The Krell door can
only passively resist the monster's power, but evidently the monster is
actually a control system capable of generating whatever power it takes to
bring its controlled variable to reference. It's a classic confrontation of
the irresistible force and the immovable object. So, as the Krell metal
turns red hot, then white hot, then blue hot and begins to flake and sag
like iron in a forge and our heros stare in horror and disbelief, I leave
you to ponder the difference between a passive equilibrium system and an
active control system. That Krell metal isn't melting from brain power.

Regards,

Bruce

3

[From Mr. Remi Cote 00H29.130896 EST

To Bruce Abbott (960812.2030 EST)

Superficially the two situations -- pressing against the wall and pressing
against your left palm -- look the same, but they are fundamentally
different.

Of course, in one case you have a passive equilibrium system, in another
you have a hierarchical passive equilibrium system.

The wall has no reference for being where it is;

I am sorry but I found this statement awfully wrong... His reference

lies in his structure, the electromagnetic force of all his molecule
combined. When you push it, there is an electromagnetic force in it
that resist your push.

There is the same kind of equilibrium in a neuron, it resist the transmi-
sion of an impulse until there is a sufficient accumulation on
electric charge.

Regards,

Mr. Remi Cote

to Rick Marken (960811.0030)

in an active control system, the disturbance to the presumed
controlled variable has almost no effect _while it is occurring_ (the speed
of rotation changes negligibly _while_ a load is applied to the shaft); in
a passive equilibrium system the disturbance to the presumed controlled
variable is fully effective _while it is occurring_ (the position of the
pendulum changes exactly as expected _while_ a push is applied to the bob).

My problem or question, were (since january): Is it possible to design a
control system within a deterministic point of view. It is possible to
design a passive equilibrium system in a way that it can "behave" (how
provocative to use this word in this net) like a control system?

If yes, I will do it with stella and triing to explain work behavior
with this model... I am already on something. As soon I'll finish
I'll let you all know, so you can criticise my point of view...

Living organisms are currently viewed as passive equilibrium systems by most
behavioral scientists.

Nope. That's not true...There after habits, some habits has nothing to do with
passive equilibrium. Like panic, pathological fear, fear of fear, all these view as
habits.

Regards, Mr. REMI

4

[From Rick Marken (960813.0930)]

Me:

in an active control system, the disturbance to the presumed controlled
variable has almost no effect _while it is occurring_

Mr. Remi Cote (00H29.130896 EST) --

My problem or question, were (since january): Is it possible to design a
control system within a deterministic point of view.

I'm not sure I know what a "deterministic point of view" is. If it's the
point of view that says we construct control systems from functional elements
[such as y = f(x)] where the value of one variable (x) determines the value
of another (y) then, "yes"; we always design control systems from a
deterministic point of view.

It is possible to design a passive equilibrium system in a way that it can
"behave" (how provocative to use this word in this net) like a control
system?

No. A passive equilibrium system will behave like a control system only when
there are no disturbances to the variable that seems to be under control by
the passive system or is under control by the control system). For example,
the position of the bob on a pendulum (a passive equilibrium system) behaves
like the position of the same bob when it is controlled by a control system
if there is no disturbance to the bob's position; in both cases,the bob just
sits there in one position. When you push on the pendulum bob, however, it
moves a distance dependent on how hard you push; when you push on the
controlled bob it moves hardly at all regardless of how hard you push.

So disturbances to (possible) controlled variables reveal the behavioral
difference between a passive equilibrium and a control system. It's a big
difference; it's not a subtle difference. But vive la difference, non?

Me:

Living organisms are currently viewed as passive equilibrium systems by most
behavioral scientists.

Remi:

Nope. That's not true...There after habits, some habits has nothing to do
with passive equilibrium. Like panic, pathological fear, fear of fear, all
these view as habits.

I meant that the basic model of behavior in psychology -- the cause-effect
model -- views behavior as a result of environmental influence rather than as
a process of controlling that environment. Passive equilibrium systems are
just a fancy version of this old cause-effect model. You seem to think that
passive equilibrium systems represent a new approach to understanding
behavior; my comment was meant to point out that you are not alone; your
(wildly incorrect, I think) belief is shared by a whole slew of fairly
well-known psychologists including Kelso, Bizzi, Turvey, Kugler, etc.

Best

Rick

5

<[Bill Leach (960812.1342 EDT)]

[From Mr. Remi Cote 00H29.130896 EST

Bruce:

Superficially the two situations -- pressing against the wall and pressing
against your left palm -- look the same, but they are fundamentally
different.

Remi:

Of course, in one case you have a passive equilibrium system, in another
you have a hierarchical passive equilibrium system.

Bruce:

The wall has no reference for being where it is;

I am sorry but I found this statement awfully wrong... His reference

lies in his structure, the electromagnetic force of all his molecule
combined. When you push it, there is an electromagnetic force in it
that resist your push.

The wall is a passive system because it does not have an energy source and a
perceptual function based control system to control the use of a source of
energy. When you push on a wall you "input" additional force(s). When your
operation is over (you stop pushing), the total energy present in the wall
has increased while the total energy in you has decreased. The wall will
have increased in thermal activity (which will return to its equilibriam
level through thermal transfer processes to the surrounding environment).
You will have used up chemical energy sources which presumably you will
replace the next time you eat.

Remi:

There is the same kind of equilibrium in a neuron, it resist the transmi-
sion of an impulse until there is a sufficient accumulation on
electric charge.

I don't know that I care for you way of wording this but I agree with what I
think you to mean. A single neuron is not a control system (not with
respect to the transmission of an output impulse -- at least that is as far
as I know anyway). A very important concept (that Bill P. often brings up)
is that a control system is a SYSTEM and that all parts of the system have
to exist. If not then you might have something that looks a lot like
control but is not.

Thus, while a COMPONENT of a control system might be a control system, that
is irrelevent to the question of whether or not the first system IS actually
a control system.

If you look at the basic control loop that we so often use here you might
note that none of the elements shown are (or at least necessarily have to
be) control systems in their own right. It is the particular organization
of necessary functions that produce a control system.

The way that we often talk about the TEST here can sometimes contribute to
misunderstanding. The TEST is used for two entirely different purposes.
The basic purpose of the TEST is to determine what variable is being
controlled by a control system. For this purpose, the TEST is an excellent
(even if often a very difficult to use) tool.

The second purpose of the TEST is to determine if we are dealing with a
control system at all. In diligent application of the TEST a negative
result does NOT mean that you are not dealing with a control system but only
that you are not dealing with a control system WITH RESPECT to the tested
variables. That is, the system that you are analyzing might still BE a
control system but if so then it is controlling something that you do not
recognize.

Any system that is found to have 1) a perceptual input function, 2) a
comparitor, 3) a reference, 4) an output function, and 5) an energy source
_could_ be a control system. If those functions are all organized a certain
way then you do have a control system. Remove any one part and you can not
have a control system.

bill leach
b.leach@worldnet.att.net
ars KB7LX

6

[Hans Blom, 960903]

(Bruce Abbott (960812.2030 EST))

Press the palm of your hand against the wall and push HARD. The
pressure exerted by your hand is transmitted into the wall, bending
the surface inward slightly, elastically compressing the material on
the near side and stretching it a bit on the back side. The force
of your push does work on the wall, storing energy in the wall until
the counterforce generated by the repulsion or attraction of the
compressed/stretched bonds equals that being developed by your hand.
All the energy going into this passive resistance comes from your
push.

Now press the palm of your right hand into the palm of your left
hand. As you press, try to prevent your right hand from moving your
left hand. Slowly increase the pressure exerted by your right hand
while still attempting to keep your left hand from moving. What
happens to the muscles in your left arm as you push harder or softer
against the left palm?

Superficially the two situations -- pressing against the wall and
pressing against your left palm -- look the same, but they are
fundamentally different. The wall has no reference for being where
it is; furthermore, all the energy necessary to resist the pressure
from your push comes from your push via the work it does in
stretching/compressing the wall material.

Some questions, Bruce, where the two situations are maybe more than
just superficially the same. Some sadism in the experimenters must be
taken for granted ;-).

Situation 1: An orthopedic surgeon mechanically fixes the angle
between the upper and the lower arm of a patient (victim?).

Situation 2: A neurosurgeon cleverly modifies and/or reroutes the
peripheral nervous system in the patient (victim?)'s arm in such a
way that the musculature controls the angle between the upper and the
lower arm at a fixed angle.

Question 1: How fundamentally different are these two situations? Can
you tell the difference if you are not allowed to look inside the arm
in any way?

Question 2: Which is the more clever solution, assuming that the
rigidity of the joint is the same in both situations?

Question 3: More generally, how can we tell whether some "black box"
is a control system or not, if control (if it is control) takes place
entirely within that black box?

Question 4: When is a controller a better solution than a mechanical
fixture?

Greetings,

Hans